The present invention relates to heat transfer decoration, as well as to the decoration of objects using a deformable pad.
A widely employed prior art method for imprinting designs onto articles using a heat transfer labelling process employs a paper base sheet or web coated with a label consisting of a release layer over which a design is imprinted in ink. In one successful technique of heat transfer decoration, labels of the above description are transferred to bottles or other articles using heat and pressure by feeding the article to a transfer site, where the preheated label-bearing web is impressed against the bottle to transfer the label. Patents illustrative of the above method and apparatus, commonly assigned with the present application, include U.S. Pat. Nos. 2,981,432; 3,064,714; 3,079,979; 3,208,897; 3,231,448; 3,261,734; and 4,214,937. This decorating technique, while highly successful in achieving high quality label transfer to bottles and similar articles, suffers certain limitations in the decoration of articles of unusual shape. Since the laminate is transferred directly to the article from a broad continuous web, this prior art process and apparatus is unsuitable for the decoration of surfaces having compound or sharp curvature. The method is therefore not easily adaptable to imprinting objects having surfaces of compound or irregular curvature or recessed panels.
Another type of apparatus which possesses special advantages in the decoration of objects of unusual conformation is the so-called pad-transfer decorator. This apparatus utilizes a resilient pad, typically comprised of a silicone elastomer. The pad receives an ink impression to be transferred to an article by pressing against an intaglio plate which had been previously coated with ink with any excess ink removed. The ink-bearing pad is then pressed against the article to be labelled, to which it imparts the ink impression. The resilient pad is adaptable to a wide variety of article conformations. This decorative method and apparatus involve assembly-line equipment of a simpler design than the above discussed heat-transfer decorators, and therefore requires fewer adjustments in retooling to articles of a variety of sizes and shapes. However, this process only transfers one color of ink at a time, and is thus slow and cumbersome if multicolored designs are required. Also since there is no protective coating covering the ink design, it is left exposed directly to the environment upon transfer to the article.
U.S. Pat. No. 3,887,420 disclsoes the use of a silicone rubber pad to transfer designs from a decorative laminate to ceramic articles. The laminate includes a base layer such as a paper sheet overlayed with a coating of wax. The wax coating is coated with a film layer (Film B), which in turn is overcoated with an ink design layer and a second film (Film A). As the laminate is heated to within a narrow ten degree temperature range, Film A is alleged to become adhesive while the wax coating and Film B become molten and nonadhesive. The transfer pad purportedly sticks to Film A when it is pressed against the laminate so that as the transfer pad is withdrawn, the substrate composed of the paper sheet and wax coating separates from the remainder of the laminate. The laminate adhering to the transfer pad is pressed onto a ceramic article, and the temperature of the laminate is dropped to within a narrow ten degree temperature range. At this temperature, Film B becomes adhesive and Film A is alleged to exhibit diminished adhesion. Thus, as the laminate is pressed onto the article with Film B contacting the article, the laminate is said to adhere to the article and released from the transfer pad as the pad is withdrawn.
The film layers A and B are each adhesive over only a very narrow ten degree temperature range, making it impractical to control the described process within the context of an automated process, since each film layer must in turn be heated or cooled to within the required ten degree temperature range to make the process workable. Precise heating or cooling of Film A and Film B to within such narrow temperature ranges is impossible to achieve or control within the split second time intervals required by an automated assembly process. This reference does not disclose the use of an independent pad heater, nor details of pad composition, surface texture, or other parameters crucial to its implementation. Furthermore, the inclusion of a wax layer to form part of the decorative substrate has the disadvantage that as the substrate is released from Film B there will be a strong tendency for a portion of the wax to remain attached to Film B. This will interfere with the adhesive characteristics of Film B as the laminate is transferred from the transfer pad to an object.
Japanese patent publication Sho No. 56-80488 discloses pad transfer decoration apparatus employing a heat-softenable transfer sheet incorporating a wax release layer, in which the article to be heated is preheated to enhance the adhesive properties of the label. This apparatus suffers the limitations of U.S. Pat. No. 3,887,420 due to the use of a wax release layer, and discloses no construction details of the decorator apparatus.
Accordingly, it is an object of the present invention to provide decorating apparatus suitable for automated transfer of labels to articles. It is a particular object of such method and apparatus that it combine the advantages of adaptability to a variety of article sizes and shapes and multicolored label capabilities.
Another object of the invention is that the apparatus be characterized by rapid and efficient operation. A related object is a multicolored decoration capability without the need for successive decorative stages.
A further object of the invention is the design of durable, reasonably inexpensive decorative apparatus. It is a further related object to avoid prolonged "down time" between decoration runs.
Yet another object of the invention is the design of decorative apparatus which is adaptable to a variety of articles. Such apparatus, for example, should be suited to the decoration of plastic, glass, and ceramic articles.
Still another object of the invention is the achievement of high quality decoration of articles. The apparatus of the invention should impart a desired image completely and without significant distortion. A particular object in this regard is the provision of high gloss images.